D:\tmp\pm>perl -Mre=debug -E"'aaaa' =~/a*a*b/"
Compiling REx "a*a*b"
synthetic stclass "ANYOF[ab]".
Final program:
1: STAR (4)
2: EXACT (0)
4: STAR (7)
5: EXACT (0)
7: EXACT (9)
9: END (0)
floating "b" at 0..9223372036854775807 (checking floating) stclass ANYOF[ab] min
len 1
Matching REx "a*a*b" against "aaaa"
Intuit: trying to determine minimum start position...
doing 'check' fbm scan, [0..4] gave -1
Did not find floating substr "b"...
Match rejected by optimizer
Freeing REx: "a*a*b"