Nothing returns a scalar in list context. If it's in list context, it will return a list. Even if it's a single element list. ;-)

Note that a failing regex in list context returning anything but an empty list would be very inconvenient, as this code is common:

if (my @matches = $var =~ /PATTERN/) {
    # match
}
else {
    # did not match
}
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If the failing match would return undef, 0, or the empty string, the result of the assignment becomes true (because a list assignment in scalar context returns the number of things on the RHS of the assignment).