re = /(?smi)^.*tag="[A-Z]_([A-Z]{2})_(\d{4}).*$/mi
str = '<?xml version="1.0"?>
-<PEGraphic gridSpaceY="100" gridSpaceX="100" bkgdImage="" gridColor="#333333" paperColor="#000000" width="19600" height="14200" version="5">
<Font height="120" name="Arial"/>
-<Polyline backFill="yes" backColor="#FFFFFF">
<Location right="6020" bottom="12445" left="6018" top="11741"/>
<Pen width="2" style="solid" color="#00FF00"/>
<Brush style="hollow" color="#00FF00"/>
<Point y="11741" x="6019"/>
<Point y="12445" x="6019"/>
</Polyline>
-<Polyline backFill="yes" backColor="#E0E0E0">
<Location right="3365" bottom="12835" left="3363" top="11741"/>
<Pen width="2" style="solid" color="#00FF00"/>
<Brush style="hollow" color="#00FF00"/>
<Point y="11741" x="3364"/>
<Point y="12835" x="3364"/>
</Polyline>
-<Polyline backFill="yes" backColor="#FFFFFF">
<Location right="4627" bottom="6800" left="4521" top="5100"/>
<Pen width="2" style="solid" color="#00FF00"/>
<Brush style="hollow" color="#00FF00"/>
<Datasource stepped="no" server="USFRPVMESPOLYOL" map="IP_DIMAP" field="VAL" tag="p_dc_1730"/>
-<Animation on="yes">
<AnimationRange color="#666666" image="" text="act sp" max="0" min="0" index="1"/>
<AnimationRange color="#00FF00" image="" text="act sp" max="1" min="1" index="2"/>
</Animation>
<Point y="5100" x="4627"/>
<Point y="6800" x="4627"/>
</Polyline>
-<Polyline backFill="yes" backColor="#FFFFFF">
<Location right="3719" bottom="4394" left="1918" top="3300"/>
<Pen width="2" style="solid" color="#00FF00"/>
<Brush style="hollow" color="#00FF00"/>
<Datasource stepped="no" server="USFRPVMESPOLYOL" map="" field="VAL" tag="P_DC_2103"/>
-<Animation on="yes">
<AnimationRange color="#666666" image="" text="act sp" max="0" min="0" index="1"/>
<AnimationRange color="#00FF00" image="" text="act sp" max="1" min="1" index="2"/>
</Animation>
<Point y="4394" x="3718"/>
<Point y="4098" x="3718"/>
<Point y="4098" x="1918"/>
<Point y="3300" x="1918"/>
</Polyline>
'
subst = 'CG $1($2)'
result = str.sub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html