use strict; open(FILE, "; close(FILE); my $oldstr = "core:para"; my $newstr = "core:para edpnum\-start\=\""; my @newlines; my $counter =0; foreach(@lines) { if ($oldstr =~ /core\:para/){ $counter = $counter +1; } $_ =~ s/$oldstr/$newstr$counter/g; push(@newlines,$_); } open(FILE, ">test.xml") || die "File not found"; print FILE @newlines; close(FILE);