$string = '|123456|john+';
/\Q$string\E/        # Strings are still interpolated,
                     # but their contents are escaped.
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$string = '|123456|john+';
/\Q$string/          # The \E is optional
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/\Q|123456|john+\E/  # As long as the text doesn't
                     # contain "$", "@", the regexp
                     # delimiter (which is "/" here)
                     # or \E.
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$string = quotemeta('|123456|john+');
/$string/
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