If the text message for the die command ends with a newline, it won't print out a line number. Consider the following:

#!/usr/bin/perl

if (@ARGV) {
    die "There was a command line parameter";
}
else {
    die "No command line stuff here.\n";
}
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When called with perl filename.pl the message is "No command line stuff here." When called with perl filename.pl foo the output is "There was a command line parameter at filename.pl line 4."