In addition to what others have said, perl also directly exposes errno via $!:

    $ perl -E 'unlink("/etc/passwd"); say (0+$!)'
    13
    $ grep 13 /usr/include/asm-generic/errno-base.h 
    #define EACCES          13      /* Permission denied */

Of course $! is a special dual-val so if you treat it as a string you get the nicer strerror(3) equivalent:

    $ perl -E 'unlink("/etc/passwd"); say $!'
    Permission denied

That said, some people prefer autodie: https://metacpan.org/pod/autodie