... or even utilise the special iteration of @ARGV ...

@ARGV = glob('*.txt');

while (<>) {
   # Do some clever stuff with $_
   # $ARGV contains the current file name
   print "$ARGV $_";
}
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or does that special operation of @ARGV only work for unadulterated i.e. non modified internally to the script, values of @ARGV ??

There you go, once again living up to my sig :D