use strict;
my $str = 'select (TRIM(TAE_TSP_REC_UPDATE)) as PK,TAE_AMT_FAIR_MV,TAE_TXT_ACCT_NUM,TAE_CDE_OWNER_TYPE,TAE_DTE_AQA_ABA,TAE_RID_OWNER,TAE_FID_OWNER,TAE_CID_OWNER,TAE_TSP_REC_UPDATE from TABLE_TAX_REP where DATE(TAE_TSP_REC_UPDATE)>=\'03/31/2018\'';
my $regex = qr@(?:\G(?!^)|\sas\s(?=.*'\d{2}/\d{2}/\d{4}'$))(?:(?!\sfrom\s).)*?\K,?\s*[A-Z_]+_(?:[FRC]ID|TSP)_[A-Z_]+@mp;
my $subst = '';
my $result = $str =~ s@$regex@$subst@rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html