Using string as array index in Perl

Question

I have run into a strange behavior in Perl that I haven't been able to find documentation for. If I (by accident) use a string as an index in an array I get the first item of the array and not undef as I would have expected.

$index = "Some string";
@array = qw(one two three);
$item = $array[$index];
print "item: " . $item;

I expected to get item: as output, but instead I get item: one. I assume that because the string doesn't start with a number it's "translated" to 0 and hence giving me the first item in the array. If the string starts with a number that part of the string seems to be used as the index.

Is this to be expected, and is there any documentation describing how strings (e.g. "2strings") are interpreted as numbers in Perl?

Answer 1

Array index imposes numeric context. The string "Some string" in numeric context is equal to 0.

Under warnings, Perl will complain

Argument "Some string" isn't numeric in array or hash lookup at ...