Cygwin bash isn't slow either. The problem is a typical bash script isn't a series of bash operations, it's a series of command line program executions.

For example, someone might do something like this (completely ignoring the need to quote in the interests of illustrating the actual issue, forking):

    for x in *; do
      new_name=$(echo $x | sed 's/old/new/')
      mv $x $new_name
    done

Instead of something like this:

    for x in *; do
      echo $x
    done | sed -r 's|(.*)old(.*)|mv \1old\2 \1new\2|' | grep '^mv ' | bash

This avoids a sed invocation per loop and eliminates self-renames, but it's harder to work with.

Of course the code as written is completely unusuable in the presence of spaces or other weird characters in filenames, do not use this.

Huh? Signals have worked fine for a long time under Cygwin.