FAQ 4.6 Why doesn't & work the way I want it to?

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4.6: Why doesn't & work the way I want it to?

    The behavior of binary arithmetic operators depends on whether they're
    used on numbers or strings. The operators treat a string as a series of
    bits and work with that (the string "3" is the bit pattern 00110011).
    The operators work with the binary form of a number (the number 3 is
    treated as the bit pattern 00000011).

    So, saying "11 & 3" performs the "and" operation on numbers (yielding
    3). Saying "11" & "3" performs the "and" operation on strings (yielding

    Most problems with "&" and "|" arise because the programmer thinks they
    have a number but really it's a string. The rest arise because the
    programmer says:

        if ("00" & "11") {
            # ...

    but a string consisting of two null bytes (the result of ""00" &
    "11"") is not a false value in Perl. You need:

        if ( ("00" & "11") !~ /[^0]/) {
            # ...


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