Three variables were defined, one in each block. (Blocks which aren't even mutually exclusive, I might add.) A fourth variable doesn't magically become defined elsewhere as a result. I believe you want

my $var;
if (...) {
   $var = ...;
}
elsif (...) {
   $var = ...;
}
else {
   die;
}
[download]

use strict;
my $zipexe;
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Three variables were defined, one in each block. (Blocks which aren't even mutually exclusive, I might add.) A fourth variable doesn't magically become defined elsewhere as a result. I believe you want

my $var;
if (...) {
   $var = ...;
}
elsif (...) {
   $var = ...;
}
else {
   die;
}
[download]

(Blocks which aren't even mutually exclusive, I might add.)

Initially I thought you meant that the blocks aren't mutually exclusive from the perspective of lexical variable scoping. It has never occurred to me that an if statement might create a single scope, rather than one for each branch. Testing seems to confirm my assumption that each branch is a separate scope.

#!/usr/local/bin/perl
use strict;
use warnings;

foreach (1..3) {
    if($_ < 2) {
        my $x = 1;
        print "$_ < 2, \$x = $x\n";
    } else {
        print "$_ >= 2, \$x = $x\n";
    }
}
__END__
Global symbol "$x" requires explicit package name at ./test.pl line 10
+.
Execution of ./test.pl aborted due to compilation errors.
[download]

Then it occurred to me that you probably mean that the conditions of the two if statements are not mutually exclusive - a possible problem with program logic but not affecting variable scope.