re = /(<Group id="\d+">\n\t\t\t<Name>)(\w+)_(\w+)(<\/Name>\n\t\t\t<Description>)([\w+\s]+)\s-\s([\w+\s]+)(<\/Description>)/m
str = ' <Group id="100">
<Name>generalAlarm_Group01</Name>
<Description>Group General Alarm 01</Description>
<Type>poll</Type>
<Content multipleGet="true">
<Param>100</Param>
<Param>101</Param>
<Param>103</Param>
<Param>104</Param>
<Param>120</Param>
<Param>121</Param>
</Content>
</Group>
<Group id="110">
<Name>generalConfig_Group01</Name>
<Description>Group General Config 01</Description>
<Type>poll</Type>
<Content multipleGet="true">
<Param>105</Param>
<Param>106</Param>
<Param>107</Param>
<Param>108</Param>
<Param>109</Param>
<Param>110</Param>
<Param>111</Param>
<Param>112</Param>
<Param>113</Param>
</Content>
</Group>
<Group id="1000">
<Name>firstPriorityAlarmConfig_Group1000</Name>
<Description>First Priority Alarm Config Table - Group 1000</Description>
<Type>poll</Type>
<Content multipleGet="true">
<Param>1000</Param>
</Content>
</Group>
<Group id="2000">
<Name>secondPriorityAlarmConfig_Group2000</Name>
<Description>Second Priority Alarm Config Table - Group 2000</Description>
<Type>poll</Type>
<Content multipleGet="true">
<Param>2000</Param>
</Content>
</Group>
<Group id="3000">
<Name>thirdPriorityAlarmConfig_Group3000</Name>
<Description>Third Priority Alarm Config Table - Group 3000</Description>
<Type>poll</Type>
<Content multipleGet="true">
<Param>3000</Param>
</Content>
</Group>'
subst = '$1$3_$2$4$6 - $5$7'
result = str.gsub(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