Change     if (grep(/^$stack$/, @stack)) { to     if (grep(/^\Q$stack$/, @stack)) {.

perlre for details.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

The start of some sanity?

In reply to Re: Problems with a regex? by BrowserUk
in thread Problems with a regex? by dwlepage

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