One way is to use the core Config module and calculate the limits from the byte size: 

    #!/usr/bin/perl -wl

    use Config;

    print $Config{intsize};

[download]
Another way, as you guessed, is with POSIX: 

    use POSIX;

    print POSIX::INT_MAX; 
    print POSIX::INT_MIN; 
    print POSIX::UINT_MAX;

[download]

Or perhaps even this: 

    print 0.5 * (-1 + unpack "I", pack "I", -1);
    print 0.5 * (-1 - unpack "I", pack "I", -1);
    print             unpack "I", pack "I", -1 ;

[download]

--
John.

In reply to Re: How to portably determine integer limits? by jmcnamara
in thread How to portably determine integer limits? by Anonymous Monk

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