Here is one part of my script:

if (PNG == 1) {
    set terminal png size 1024,768 font "Arial,11"
    SAVE_AS = FILENAME.'.png'
    print "    - Create file: ".SAVE_AS
    set output SAVE_AS
    plot DATA_FILE using ($1/3600.0):(column('POW-FP+D')) with lines title 'POW-FP+D' linecolor rgb "red" axis x1y1,
         DATA_FILE using ($1/3600.0):(column('PR-Core')) with lines title 'PR-Core' linecolor rgb "blue" axis x1y2
}

if (SVG == 1) {
     set term svg size 600,400 dynamic font 'Arial,11'
     SAVE_AS = FILENAME.'.svg'
     print "    - Create file: ".SAVE_AS
     set output SAVE_AS
    plot DATA_FILE using ($1/3600.0):(column('POW-FP+D')) with lines title 'POW-FP+D' linecolor rgb "red" axis x1y1,
         DATA_FILE using ($1/3600.0):(column('PR-Core')) with lines title 'PR-Core' linecolor rgb "blue" axis x1y2
}

As you can see the plot DATA_FILE … occures two times in my code, once in the PNG-part and once in the SVG-part. Is it possible to put the code in some kind of a variable and then refere to this variable. Here some pseudo-code:

a = DATA_FILE using ($1/3600.0):(column('POW-FP+D')) with lines title 'POW-FP+D' linecolor rgb "red" axis x1y1,
    DATA_FILE using ($1/3600.0):(column('PR-Core')) with lines title 'PR-Core' linecolor rgb "blue" axis x1y2

if (PNG == 1) {
    ...
    plot a
}

if (SVG == 1) {
     ...
    plot a
}