I was thinking of the following contexts | examples:

c:\@Work\Perl>perl -wMstrict -le "print '>', !1, '<';"
><
c:\@Work\Perl>perl -wMstrict -le "print '>', !1 && 1, '<';"
><
[download]

In numeric contexts such as that supplied by the  %b printf format specifier, !1 will, I think, always evaluate to numeric 0 — but it would be best to do some research on this!