Your dec has a problem. Anything matched by /^[0-7]+$/ or /^\d+$/ is going to be matched by /^(0x)?[0-9A-Fa-f]+$/i as well, so if you do the tests in order you present it, it'll assume either hexadecimal, or binary. Reversing the order will give a problem as well. How would you distinguish between 10₁₆ == 16₁₀, 10₁₀, and 10₈ == 8₁₀ (subscripts indicate base)?

Of course, as pointed out, your fallacy lies in assuming that oct and hex return decimal representations of numbers - they don't. They return numbers:

    $ perl -MDevel::Peek -wle 'Dump hex 10'
    SV = IV(0x8192014) at 0x8181270
      REFCNT = 1
      FLAGS = (IOK,READONLY,pIOK)
      IV = 16
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It's a number - without a stringified valued.

Also, Perl already has a function to turn a number into a hexadecimal, octal or binary representation: it's called sprintf.

Abigail