$ perl -le'print ~0'
18446744073709551615

$ perl -Mbigint -le'print +( 2 ** 64 ) - 1'
18446744073709551615

$ perl -le'print +( 2 ** 64 ) - 1'
1.84467440737096e+19


##</code><code>##

$ perl -le'print 2 ** 49'
562949953421312

$ perl -le'print 2 ** 50'
1.12589990684262e+15