If $image is '' or undefined, then $file would be "F:/images/". If the directory F:/images exists, then -e would be true. If you used "use warnings;" you'd at least get a warning in the undefined case.

I'd suggest also using -f instead of -e, as -f would be true only if it exists and is a file rather than a directory:

$ perl u.pl
Use of uninitialized value $file in concatenation (.) or string at u.p
+l line 16.
Use of uninitialized value $file in concatenation (.) or string at u.p
+l line 21.
OK, missing
OK, missing
OK, OK
$ cat u.pl
use strict;
use warnings;

my $f1;
my $f2='';
my $f3='README';

my $dir='./xyz';

print chk($dir, $f1), ", ", chk2($dir,$f1),"\n";
print chk($dir, $f2), ", ", chk2($dir,$f2),"\n";
print chk($dir, $f3), ", ", chk2($dir,$f3),"\n";

sub chk {
    my ($dir, $file) = @_;
    return -e "$dir/$file" ? "OK" : "missing";
}

sub chk2 {
    my ($dir, $file) = @_;
    return -f "$dir/$file" ? "OK" : "missing";
}
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...roboticus

When your only tool is a hammer, all problems look like your thumb.