Unfortunately that just isn't the way perl defines things. Perl has no distinction between float/int - not even when int() function is used. Perl scalars essentially have 3 basic flavours: number/string/reference. Inf and NaN are valid numbers in perl, and int() returns a number. Hence why they don't see anything wrong with int() returning Inf/Nan.

That's not correct. Perl internals *do* distinguish between signed/unsigned ints, floats, and strings. Aside from internals, there *isn't* a distinction between numbers and strings, but every perl operator gets to decide how it will coerce its input, and the operators do generally fall into categories of "number operators" and "string operators", but nothing forces that convention.

Against that backdrop, and the existence of the "use integer" pragma, I would expect a function named "int" to always cast its argument to an integer, or maybe 'undef' for failures.

perl -E 'my $x= "NaN"; say $x+0; say int($x); { use integer; say $x+0 
+}'
NaN
NaN
0
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I sincerely doubt this has anything to do with perl's decline. JavaScript and PHP have ten times as many shoddy API edge cases.