The error message is coming directly from gzcat. The open() call succeeded.

If you need to verify the existence of the file, check that before you open the pipe. e.g.:

my $file = '/home/me/file.zip.gz';
die "no such file '$file'" unless -f $file;
my $cmd = "gzcat $file |";
open(IN, $cmd) or die "open failed: $!";
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