ifs.assert==PLA||s.assert==NLA{// Lookahead - return true (or false) if at least one match starts at 0. Zero is used because the test-string _starts_ from idx.
ifmatchIdx[0].startIdx ==0{
ifmatchIdx[0].StartIdx ==0{
numMatchesFound++
}
}
ifs.assert==PLB||s.assert==NLB{// Lookbehind - return true (or false) if at least one match _ends_ at the current index.