use strict; use warnings; use IO::InSitu; my $infile_name = 'fred.tmp'; my $outfile_name = $infile_name; my ($in, $out) = open_rw($infile_name, $outfile_name); for my $line (<$in>) { print {$out} transform($line); } # Try pressing CTRL-C while file is being updated. sub transform { sleep 1; return "hello:" . $_[0]; }