Are you sure both stat calls succeed? If you use strictures (use strict; use warnings;) you'll be getting "Use of uninitialized value" warnings. Given that you reprise the stat calls later why not do them up front and check success? Something like:

sub cftsain {
    # Copy the image file if not there or changed.

    my ($xxfn1, $xxfn2) = @_;
    my @dd = (0, $xxfn1, $xxfn2, (stat "$xxfn1")[9], (stat "$xxfn2")[9
+]);

    die "Can't stat '$xxfn1'. Maybe it's missing?" if ! defined $dd[3]
+;
    
    if (!-e $xxfn2) {
        ...
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