Increment avoids warning unexpectedly

jesuashok has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Increment avoids warning unexpectedly by davido (Cardinal) on Jun 07, 2006 at 16:36 UTC
The pre-increment and post-increment operators are designed to work on strings too. Witness the following: `my $string = "abc"; print ++$string, "\n";` [download] If my calculations are correct, you should see "abd". So the point is that if you give ++ a string that it can figure out, it will increment it. Thus, non-numeric strings are legal arguments for ++. Now, in your case, you gave the increment operator a string that it couldn't sensibly increment in its non-numeric form, so the ++ operator dropped into numeric form, and incremented 0 to 1. No warning because non-numeric strings are legal in this case. To read more about the ++ operator's "magic", see perlop. Dave	[reply] [d/l]
Re^2: Increment avoids warning unexpectedly by ikegami (Patriarch) on Jun 07, 2006 at 17:23 UTC
I see two holes in your argument. 1) That particular string is non-numeric and it does get converted to numeric. What would be the point of not issuing a "non-numeric isn't numeric" warning when it happens because the operator works with some other strings? 2) `perl -wle "$s='abc'; $s--; print $s"` doesn't give a warning either, yet non-numeric strings are never legal for the post-decrement operator. I suspect the warning is surpressed as a side-effect (intentional or not) of supressing the undefined warning when executing `my $i; $i++;`.	[reply] [d/l] [select]
Re^2: Increment avoids warning unexpectedly by jpeg (Chaplain) on Jun 07, 2006 at 16:45 UTC
However, the ++'s operator's magic applies to strings that `=~ m/^[a-zA-Z][0-9]\z/`. "a,b" doesn't match. I suspect that in the third case perl is calling int($m), which returns 0, then applying the prefix increment operator. Code tags added by GrandFather -- jpg	[reply] [d/l]
Re^2: Increment avoids warning unexpectedly by Hue-Bond (Priest) on Jun 23, 2006 at 22:00 UTC
non-numeric strings are legal arguments for ++ `++` works even on undefined values: `$ /usr/bin/perl -le'print $a++' 0` [download] -- David Serrano	[reply] [d/l]
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Re: Increment avoids warning unexpectedly by MonkE (Hermit) on Jun 07, 2006 at 17:07 UTC
The autoincremenet operator is "magical", see perlman:perlop for more details. Try adding the following code to your test program to see the magic at work: `$m="acb"; print ++$m; # Prints acc, as expected (according to perlop) # and throws no warning ... wierd huh?` [download]	[reply] [d/l]