Reading two lines of data from a file - perl

Question

I have a file which I would like to read data from. This is a sample of the data:
NODELOAD 28 27132 3.29108E+04 7.94536E+04 0.00000E+00
NODELOAD 29 27083 9.89950E+04 9.89950E+04 0.00000E+00
NODELOAD 29 27132 6.08112E+04 6.08112E+04 0.00000E+00
NODELOAD 30 27083 1.29343E+05 5.35757E+04 0.00000E+00
NODELOAD 30 27132 7.94536E+04 3.29108E+04 0.00000E+00
NODELOAD 31 68 4.80185E+04 -5.47647E+04 -1.17033E+04
-1.27646E+03 1.18350E+04 -2.03885E+03
NODELOAD 31 1114 1.20706E+05 -3.31323E+04 -7.17280E+04
2.28198E+03 2.75582E+04 5.74460E+02
I have this code and am able to read all values of a single line and save them to an array:
foreach my $line (#input) {
if($line =~ /^\s*NODELOAD\s+/i) {
$line =~ s/^\s*//;
#a = split(/\s+/,$line);
$modelData{"NODELOAD"}->{$a[1]}->{$a[2]}->{"Fx"} = $a[3];
$modelData{"NODELOAD"}->{$a[1]}->{$a[2]}->{"Fy"} = $a[4];
$modelData{"NODELOAD"}->{$a[1]}->{$a[2]}->{"Fz"} = $a[5];
However, there are some "NODELOAD" definitions in the file that are defined on two lines and have 6 load values instead of 3 (the first two numbers on each line are identifiers, the following 3/6 are data).
Is it easiest writing an if statement, which saves the data if the following line does not begin with "NODELOAD" and contains numbers? The very last line after this part in the text file will not contain any numbers, but may be blank or contain text.

Answer 1

Yes, the easiest approach would be to keep values from previous call in some variable, then if if(/NODELOAD/) doesn't match, you get just 3 values and process them using identifiers from previous line (and previous look iteration). You could also skip a regexp in if, and check for the first element of split result:
my #last_values;
foreach my $line (#input) {
$line =~ s/^\s+//;
my #values = split(/\s+/, $line);
if( $values[0] ne 'NODELOAD' ) {
unshift( #values, #last_values[0..2] ); # Get first 3 values from previous call
# Then process it however you'd like to
$modelData{"NODELOAD"}->{$values[1]}->{$values[2]}->{"Fx2"} = $values[3];
}
elsif {
# process like previously...
$modelData{"NODELOAD"}->{$values[1]}->{$values[2]}->{"Fx"} = $values[3];
$modelData{"NODELOAD"}->{$values[1]}->{$values[2]}->{"Fy"} = $values[4];
$modelData{"NODELOAD"}->{$values[1]}->{$values[2]}->{"Fz"} = $values[5];
#last_values = #values; # and save for future reference
}
}