diff --git a/compiler/ast_to_ir.py b/compiler/ast_to_ir.py
index 8d6f755a4..c1e753fa3 100644
--- a/compiler/ast_to_ir.py
+++ b/compiler/ast_to_ir.py
@@ -8,6 +8,8 @@
 from util import *
 from parse import from_ast_objects_to_shell
 
+from custom_error import *
+
 ## TODO: Separate the ir stuff to the bare minimum and
 ##       try to move this to the shell_ast folder.
 
@@ -159,7 +161,7 @@ def combine_pipe(ast_nodes):
     else:
         ## If any part of the pipe is not an IR, the compilation must fail.
         log("Node: {} is not pure".format(ast_nodes[0]))
-        raise Exception("Not pure node in pipe")
+        raise UnparallelizableError("Node: {} is not a pure node in pipe".format(ast_nodes[0]))
 
     ## Combine the rest of the nodes
     for ast_node in ast_nodes[1:]:
@@ -168,7 +170,7 @@ def combine_pipe(ast_nodes):
         else:
             ## If any part of the pipe is not an IR, the compilation must fail.
             log("Node: {} is not pure".format(ast_nodes))
-            raise Exception("Not pure node in pipe")
+            raise UnparallelizableError("This specific node: {} is not a pure node in pipe".format(ast_node))
 
     return [combined_nodes]
 
diff --git a/compiler/custom_error.py b/compiler/custom_error.py
new file mode 100644
index 000000000..eedb6f738
--- /dev/null
+++ b/compiler/custom_error.py
@@ -0,0 +1,5 @@
+class UnparallelizableError(Exception):
+    pass
+
+class AdjLineNotImplementedError(Exception):
+    pass
\ No newline at end of file
diff --git a/compiler/ir.py b/compiler/ir.py
index c1534494a..b7319cc23 100644
--- a/compiler/ir.py
+++ b/compiler/ir.py
@@ -38,6 +38,7 @@
 
 from shell_ast.ast_util import *
 from util import *
+from custom_error import *
 
 import config
 
@@ -242,11 +243,11 @@ def compile_command_to_DFG(fileIdGen, command, options, redirections=None):
         command_invocation
     )
     if io_info is None:
-        raise Exception(
+        raise UnparallelizableError(
             f"InputOutputInformation for {format_arg_chars(command)} not provided so considered side-effectful."
         )
     if io_info.has_other_outputs():
-        raise Exception(
+        raise UnparallelizableError(
             f"Command {format_arg_chars(command)} has outputs other than streaming."
         )
     para_info: ParallelizabilityInfo = (
@@ -840,7 +841,7 @@ def apply_parallelization_to_node(
                 node_id, parallelizer, fileIdGen, fan_out
             )
         else:
-            raise Exception("Splitter not yet implemented")
+            raise UnparallelizableError("Splitter not yet implemented for command: {}".format(self.get_node(node_id=node_id).cmd_invocation_with_io_vars.cmd_name))
 
     def apply_round_robin_parallelization_to_node(
         self, node_id, parallelizer, fileIdGen, fan_out, r_split_batch_size
@@ -849,11 +850,11 @@ def apply_round_robin_parallelization_to_node(
         #  currently, this cannot be done since splitter etc. would be added...
         aggregator_spec = parallelizer.get_aggregator_spec()
         if aggregator_spec.is_aggregator_spec_adj_lines_merge():
-            raise Exception("adj_lines_merge not yet implemented in PaSh")
+            raise AdjLineNotImplementedError("adj_lines_merge not yet implemented in PaSh")
         elif aggregator_spec.is_aggregator_spec_adj_lines_seq():
-            raise Exception("adj_lines_seq not yet implemented in PaSh")
+            raise AdjLineNotImplementedError("adj_lines_seq not yet implemented in PaSh")
         elif aggregator_spec.is_aggregator_spec_adj_lines_func():
-            raise Exception("adj_lines_func not yet implemented in PaSh")
+            raise AdjLineNotImplementedError("adj_lines_func not yet implemented in PaSh")
         # END of what to move
 
         node = self.get_node(node_id)
@@ -1192,7 +1193,7 @@ def introduce_aggregators_for_consec_chunks(
                     fileIdGen,
                 )
             else:
-                raise Exception("aggregator kind not yet implemented")
+                raise UnparallelizableError("aggregator kind not yet implemented for command: {}".format(original_cmd_invocation_with_io_vars.cmd_name))
         else:  # we got auxiliary information
             assert parallelizer.core_aggregator_spec.is_aggregator_spec_custom_2_ary()
             map_in_aggregator_ids = in_aggregator_ids
diff --git a/compiler/pash_compiler.py b/compiler/pash_compiler.py
index c4fc7282e..a949457ba 100644
--- a/compiler/pash_compiler.py
+++ b/compiler/pash_compiler.py
@@ -4,6 +4,7 @@
 from datetime import datetime
 
 from sh_expand import env_vars_util
+from sh_expand.expand import ExpansionError 
 
 import config
 from ir import *
@@ -11,6 +12,7 @@
 from ir_to_ast import to_shell
 from pash_graphviz import maybe_generate_graphviz
 from util import *
+from custom_error import *
 
 from definitions.ir.aggregator_node import *
 
@@ -92,9 +94,17 @@ def compile_ir(ir_filename, compiled_script_file, args, compiler_config):
         ret = compile_optimize_output_script(
             ir_filename, compiled_script_file, args, compiler_config
         )
+    except ExpansionError as e: 
+        log("WARNING: Exception caught because some region(s) are not expandable and therefore unparallelizable:", e) 
+    except UnparallelizableError as e: 
+        log("WARNING: Exception caught because some region(s) are unparallelizable:", e) 
+        # log(traceback.format_exc()) # uncomment for exact trace report (PaSh user should see informative messages for unparellizable regions) 
+    except (AdjLineNotImplementedError, NotImplementedError) as e: 
+        log("WARNING: Exception caught because some part is not implemented:", e)
+        log(traceback.format_exc())
     except Exception as e:
         log("WARNING: Exception caught:", e)
-        # traceback.print_exc()
+        log(traceback.format_exc())
 
     return ret
 
@@ -142,7 +152,7 @@ def compile_optimize_output_script(
 
         ret = optimized_ast_or_ir
     else:
-        raise Exception("Script failed to compile!")
+        raise UnparallelizableError("Script failed to compile!")
 
     return ret