So, if I ask to convert "55a" then it returns "55" which is fine. But if I try to convert "a55" then it returns 0, which baffles me! It should return 55. Why does this happen?

This is simply how Perl's string-to-number conversion works, it only takes the first portion of the string that looks like a number (although interestingly, I'm having trouble finding a reference in the Perl documentation at the moment*). The tr/0-9//cd solution is one way to work around that, if you are ok with strings such as "a1b2c3.4d" being converted to 1234.

local $SIG{__WARN__}

Instead of trying to trap the warning, it's better to use looks_like_number from Scalar::Util, as this gives you the exact internal function that Perl uses to check strings and generate that warning in the first place. (Update 2: We've been over this before.)

* Update: The Camel says "To convert from string to number, Perl internally uses something like the C library’s atof(3) function.", and atof(3) says "The atof() function converts the initial portion of the string" (emphasis mine).

In reply to Re: Converting to number doesn't always work... (updated) by haukex
in thread Converting to number doesn't always work... by harangzsolt33

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