In many real-world cases ... and yours is no exception ... an input file consists of various “lines” which have a recognizable and useful pattern. Generally, some line marks the beginning of a group of records, another line marks the end, and the rest (which might have a less-recognized pattern) can simply be handled by an “everything else” case. The awk tool was based on this simple notion, and Perl more-or-less evolved from it. So, here is a general sketch of a good approach – extemporaneous and untested:
my @lines = [];
#
# THE MAIN PROGRAM READS THE FILE LINE-BY-LINE, CLASSIFYING THEM
# USING REGULAR EXPRESSIONS
#
while(<>) {
if (/^\<SUBBEGIN) { # STARTING LINE
@lines = [];
}
elsif(/^<SUBEND/) { # ENDING LINE
look_for_patterns();
}
# INSERT "elsif" CASES HERE TO FILTER OUT BLANK LINES
# OR OTHER UNWANTED "JUNK," IF APPLICABLE ...
#
else { # "EVERYTHING ELSE"
push @lines, $_
}
}
look_for_patterns(); # IF APPROPRIATE – MAY NOT BE, FOR THIS CASE
# THIS SUBROUTINE EXAMINES EACH ACCUMULATED GROUP OF LINES
# LOOKING TO SEE IF BOTH DESIRED PATTERNS ARE INSIDE.
sub look_for_patterns {
my $CFU_seen = 0;
my $CFB_seen = 0;
foreach (@lines) {
if (/CFU-TS10-ACT/) {
$CFU_seen = 1;
}
elsif (/CFB-TS10-ACT/) {
$CFB_seen = 1;
}
}
if ($CFU_seen && $CFB_seen) print "Yay!\n";
}
The first block in this completely extemporaneous code example is a simple, awk-like loop which classifies lines. The second subroutine then loops through the most-recent set of lines that have been accumulated. (This subroutine is called each time an ending-record is found, and maybe also(!) at end-of-file.)
For what it’s worth, I no longer use awk to solve such problems, although a comparison between this and an awk solution may be instructive. (There is, in fact, an a2p tool which directly translates “awk 2 perl.”) But this is a time-tested and classic approach for dealing with a use-case which is so very common that it inspired the creation of at least two legendary and venerable software tools.
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