Something like:

my %ignorables = map { $_ => 1 } qw([notice mpmstats: rdy bsy rd wr ka
+ log dns cls bsy: in);  

open my $error_fh, '<', 'iset_error_log';   

sub findLines {
    # Iterates over the lines in the file, putting each into $_ 
    my @all_lines;
    while (<$error_fh>) {      
        
        # Only worry about the lines containing [notice     
        if (/\[notice/) {          
            
            if (/\brdy\b/){
                print "\n";
            }
            else {
                print ",";
            }
            
     
            my @line = grep { not defined $ignorables{$_} } split /\s+
+/;          
            
            # Cleanup         
            s/|^\[|notice|[]]//g for @line; # remove [ from [foo   
            
            # Output the line         
            @line = join(",", @line);          
            s/,,/,/g for @line;
            print @line; #this is where I would like to return the arr
+ay.
                        push @all_lines, @lines;
            }
        } 
        return @all_lines; # outside of while loop
    }  

&findLines;

close $error_fh;
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