c:\@Work\Perl>perl -wMstrict -le
"for ('filesystem          kbytes   used     avail    capacity  mounted on',
      '/dev/dsk/c0b0t0d0s4 12209400 5496486  6712914  46%       /home',
   ) {
   printf qq{'%s' -> '%s' \n}, $_, parse_capacity($_);
   }
 ;;
 sub parse_capacity {
   my ($df_output) = @_;
   return $df_output =~ m[(\d+)%\s+/home$] ? $1 : 'Match Error';
   }
"
'filesystem          kbytes   used     avail    capacity  mounted on' -> 'Match Error'
'/dev/dsk/c0b0t0d0s4 12209400 5496486  6712914  46%       /home' -> '46'