defined($var)==0
Use of uninitialized value in numeric eq (==)

use strict;
use warnings;

my $variable = undef;

if( undef == 0 ){
    print "undef == 0\n";
}

if( $variable == 0 ){
    print "\$variable undef == 0\n";
}

if( "" == 0 ){
    print "\"\" == 0\n";
}

if( undef eq 0 ){
    print "undef eq 0\n";
}

if( undef eq 0 ){
    print "\$variable undef eq 0\n";
}

if( undef eq "" ){
    print "undef == \"\" \n";
}

if( 0 == "0" ){
    print "0 == \"0\"\n";
}

if( 0 eq "" ){
    print "0 eq \"\"";
}

if( undef eq "" ){
    print "undef == \"\"\n";
}

if( defined ($variable) eq "" ){
    print "undef == \"\"\n";
}

exit 0;

[download]
The last two cases may be of particular interest. undef is uninitialized as itself or from a variable, but as the result of defined it is not uninitialized. Magic conditions. I'm running Perl 5.26.1

Nvm: doy. Defined returns "" on undef.

In reply to Re^8: Regex result being defined when it shouldn't be(?) by chenhonkhonk
in thread Regex result being defined when it shouldn't be(?) by chenhonkhonk

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