Example usages:

Without quotemeta, the following would not match. It would try (and fail) to match a digit.

$not_a_regexp = '\\d';                            # The 2 chars: \d
$not_a_regexp_quoted = quotemeta($not_a_regexp);  # The 3 chars: \\d
$not_a_regexp =~ /^$not_a_regexp_quoted\z/;       # Matches.
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Without quotemeta, eval would try to execute '''., which is invalid Perl.

$not_code = "'";                          # '
$not_code_quoted = quotemeta($not_code);  # \'
$string = eval "'$not_code'";             # '
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