Can a latex IF loop take a perl variable?

Question

I have a script written in perl which harvest data from an sql database, then produces a printed report in latex.

I was looking to put an IF loop in the latex part of the script to print one set of text if the data existed in the sql database, and a different set of text if it does not.

Looks like etoolbox is promising here, but can it take a variable (which I can set to be anything - 1,0,T,F etc)?

I found this example on the site which shows how to set up the loop but without a variable (LaTeX conditional expression).

\newtoggle{paper}

which is set with either

\toggletrue{paper}
\togglefalse{paper}

And to use it:

\iftoggle{paper}{%
  % using paper
}{%
  % electronic
}

EDIT: What I am wondering is if I can use a variable from earlier in my script (e.g. $myo_text) in the eftoolbox toggle.

e.g.

\newtoggle{$myo_text}

Or is there another way of doing this? Is it even possible to carry a variable into the latex part of the script from the sql query and use it in a conditional loop?

EDIT 2: Here is a trimmed latex chunk from my script. Just now it prints out these perl variables just fine ($myo_test, $myo_reporter1 etc).

print FH <<END;

\\textbf{EXERCISE TOLERANCE TEST} \\newline
\\begin{small}
\\textbf{Stress Test:} $myo_test \\newline
\\textbf{Rest ECG:} $myx_rest_ecg \\newline
\\textbf{Stress ECG:} $myx_stress_ecg \\newline  
\\textbf{Performed by:} $myx_performed1 \\newline
\\end{small}

\\textbf{Reported By:} $myo_reporter1 \\hspace{2em} \\textbf{Signature:}

\\end{document}


END

I would like to put a loop in this latex chunk that does not print this part of the report if $myo_text is blank/empty.

Answer 1

LaTeX has no knowledge of the perl variables, you just need to write the correct latex. In general it's probably best to test in the perl and then just write appropriate latex

something like

if($myo_test !="") {

print FH <<END;

\\textbf{EXERCISE TOLERANCE TEST} \\newline
\\begin{small}
\\textbf{Stress Test:} $myo_test \\newline
\\textbf{Rest ECG:} $myx_rest_ecg \\newline
\\textbf{Stress ECG:} $myx_stress_ecg \\newline  
\\textbf{Performed by:} $myx_performed1 \\newline
\\end{small}

\\textbf{Reported By:} $myo_reporter1 \\hspace{2em} \\textbf{Signature:}

END

}

but you could use any latex test for empty eg \ifx\relax..\relax and do simple tests in the latex

print FH <<END;
\\ifx\\relax$myo_test\\relax
\\else
\\textbf{EXERCISE TOLERANCE TEST} \\newline
\\begin{small}
\\textbf{Stress Test:} $myo_test \\newline
\\textbf{Rest ECG:} $myx_rest_ecg \\newline
\\textbf{Stress ECG:} $myx_stress_ecg \\newline  
\\textbf{Performed by:} $myx_performed1 \\newline
\\end{small}
\\fi

\\textbf{Reported By:} $myo_reporter1 \\hspace{2em} \\textbf{Signature:}


\\end{document}


END

But in either style there is no sense in which latex is accessing the perl variable, perl is just writing out a static file to be processed later by latex.