And the B::Deparse module can be handy when trying to figure out why when something's not behaving the way you expect. I show running over code given in a shell here-doc, but you can do the same thing to code in a file via perl -MO=Deparse,-p my_file.plx.

$ perl -MO=Deparse,-p <<'EOT'
if ($answer eq "add" || "a") {
&addlinks;
} elsif ($answer eq "remove" || "r") {
&rmlinks;
} else {exit 0;
}
EOT
if ((($answer eq 'add') or 'a')) {
    &addlinks;
}
elsif ((($answer eq 'remove') or 'r')) {
    &rmlinks;
}
else {
    exit(0);
}
- syntax OK
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In the explicitly parenthesized version you can see exactly what your comparisons really mean to Perl.