Yes. This considers 1 as TRUE and 0 as FALSE:

use warnings;
use strict;

my $i = 0;
while (foo($i)) {
    print "i = $i\n";
    $i++;
}

sub foo {
    my $x = shift;
    return ($x < 5) ? 1 : 0;
}

__END__
i = 0
i = 1
i = 2
i = 3
i = 4
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