open HAN, "It" || die "No file";
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this means:

open HAN, ( "It" || die "No file" );
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so this will never fail as long as the string "IT" is true. If you really want to use ||, use parantheses around:

open( HAN, "It" ) || die "No file";
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or use "or" instead (which is IMHO better readable:

open( HAN, "It" ) or die "No file";
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