Perl 5 version 8.9 documentation
Returns the value of EXPR with all non-"word" characters backslashed. (That is, all characters not matching
/[A-Za-z_0-9]/will be preceded by a backslash in the returned string, regardless of any locale settings.) This is the internal function implementing the
\Qescape in double-quoted strings.
If EXPR is omitted, uses